PWL REPEAT FOR + REPEAT FOREVER

Author: marcin-golebiowski

README.md

@@ -128,7 +128,7 @@ LTspice mode covers syntax such as:
 - `.backanno` and selected output/viewer options as warning no-ops
 - one-argument `.TRAN` with a derived step policy
 - scalar expression aliases, `table(...)` / `tbl(...)`, and smooth limiters `uplim(...)` / `dnlim(...)`
-- source waveforms including `EXP(...)`, finite-cycle `PULSE(... Ncycles)`, finite-cycle `SINE(... Ncycles)`, and local two-column `PWL file=<path>` data
+- source waveforms including `EXP(...)`, finite-cycle `PULSE(... Ncycles)`, finite-cycle `SINE(... Ncycles)`, local two-column `PWL file=<path>` data, and simple LTspice `PWL REPEAT FOR` / `REPEAT FOREVER` blocks
 - independent-source topology options: `Rser`, `Cpar`, `load`, and `R=<value>`
 - model parameter aliases: resistor and capacitor models accept `tc=<tc1>[,<tc2>]`; voltage switches accept `von` / `voff`; current switches accept `ion` / `ioff`
 - switch model series options `Vser` and `Lser`

roadmap/ltspice-compatibility-matrix.md

@@ -1,6 +1,6 @@
 ---
 title: LTspice Compatibility Matrix
-status: P3 Baseline + .FOUR Support Refresh + Custom Passives + Ideal Diodes + Golden Evidence + Include/Lib Path Evidence + Waveform Docs Refresh + PWL Text Variants + Finite SINE + Source/R-C/L Parasitics
+status: P3 Baseline + .FOUR Support Refresh + Custom Passives + Ideal Diodes + Golden Evidence + Include/Lib Path Evidence + Waveform Docs Refresh + PWL Text Variants + PWL Repeat Variants + Finite SINE + Source/R-C/L Parasitics
 scope: SpiceSharpParser + SpiceSharp
 last_reviewed: 2026-07-07
 ---
@@ -58,7 +58,8 @@ Compatibility classes:
 | `EXP(...)` source waveform | Accepted | Produces internal exponential waveform | TRAN supported | Analytic fixture plus optional LTspice-backed transient golden | Invalid count/tau diagnostics name `EXP` | Current parser/runtime | P2 supports the six-argument form `EXP(v1 v2 td1 tau1 td2 tau2)`. |
 | `PULSE(... Ncycles)` | Accepted in LTspice mode | Produces finite-cycle pulse waveform | TRAN supported | Analytic transient fixture plus optional LTspice-backed transient golden | Invalid period or cycle count produces targeted `PULSE` diagnostic | Current parser/runtime | The eighth LTspice argument limits the waveform to `Ncycles` periods, then returns to the initial value. |
 | `SINE(... Ncycles)` | Accepted in LTspice mode | Produces finite-cycle sine waveform | TRAN supported | Analytic transient fixture plus optional LTspice-backed transient golden | Invalid frequency or cycle count produces targeted `SINE` diagnostic | Current parser/runtime | The seventh LTspice argument limits the waveform to `Ncycles` periods after the delay, then returns to the offset value. |
-| `PWL file=<path>` source waveform | Accepted | Produces PWL waveform from a local two-column text file with optional header row | TRAN supported | Analytic transient fixture | Missing file, empty file, no data rows, malformed rows, and unsupported LTspice repeat forms produce targeted `PWL` diagnostics | Current parser/runtime | File data may start after leading blank lines or full-line comments beginning with `;`, `#`, `*`, or `//`; space, comma, semicolon, and tab delimiters are fixture-backed. Broader LTspice PWL repeat variants are deferred. |
+| `PWL file=<path>` source waveform | Accepted | Produces PWL waveform from a local two-column text file with optional header row | TRAN supported | Analytic transient fixture | Missing file, empty file, no data rows, and malformed rows produce targeted `PWL` diagnostics | Current parser/runtime | File data may start after leading blank lines or full-line comments beginning with `;`, `#`, `*`, or `//`; space, comma, semicolon, and tab delimiters are fixture-backed. |
+| `PWL REPEAT FOR <n>` / `REPEAT FOREVER` | Accepted in LTspice mode | Produces finite expanded PWL or runtime repeating PWL waveform | TRAN supported | Analytic transient fixture plus optional LTspice-backed transient golden for `REPEAT FOR` | Bare `REPEAT`, missing `ENDREPEAT`, bad repeat count, odd point data, non-increasing local times, contradictory zero-time boundaries, nested repeats, trailing parameters after `ENDREPEAT`, and unsupported combined forms produce targeted `PWL` diagnostics | Current parser/runtime | Supports simple non-nested repeat blocks with local repeat times. Time/value scale factors, `SCOPEDATA`, trigger restarts, relative `+time` points, and nested/combined PWL specs remain deferred. |
 | Independent source `tbl=(expr,x1,y1,...)` | Accepted in LTspice mode | Lowered to behavioral `table(...)` source | OP supported | Analytic fixture | Invalid form names `tbl` | Current parser/runtime | Parser shim uses the existing source/table expression path. |
 | Source `wavefile=<path> chan=<n> [amplitude=<value>]` | Accepted | Produces wave-file waveform | Existing wave-file behavior | Smoke/diagnostic fixture | Missing `wavefile`, missing `chan`, missing file, and invalid `chan` produce targeted validation | Current parser/runtime | Channel defaults are not inferred. |
 | Source `Rser`, `Cpar`, `load`, `R=<value>` | Accepted | Synthesizes helper R/C entities in LTspice mode | OP supported for resistance helpers; Cpar read fixture | Analytic/parser fixture plus optional LTspice-backed OP golden | Malformed value forms produce targeted LTspice source-option diagnostics | Current parser/runtime | Parser-only topology synthesis: `Rser` adds a series resistor, `Cpar` adds a shunt capacitor, `load` adds a shunt resistor, and `R=<value>` maps to series resistance on voltage sources and load resistance on current sources. Core source models are unchanged. |

roadmap/ltspice-netlist-compatibility-plan.md

@@ -38,7 +38,7 @@ This roadmap is intentionally parser-first and evidence-first:
 - `.TRAN` accepts traditional numeric forms and trailing `UIC`; P1 LTspice mode also accepts `.tran <Tstop>` and `.tran <Tstop> UIC` by deriving `step = Tstop / 50.0`. LTspice `startup`, `steady`, `nodiscard`, and `step` modifiers remain targeted errors.
 - LTspice output/viewer `.options` such as `plotwinsize`, `plotreltol`, `plotvntol`, `plotabstol`, `numdgt`, `measdgt`, `meascplxfmt`, `baudrate`, and `fastaccess` are warning no-ops only in LTspice mode.
 - LTspice behavior-changing `.options` such as `cshunt`, `gshunt`, `srcsteps`, `gminsteps`, `trtol`, `chgtol`, `pivrel`, `pivtol`, and `ptrantau` remain targeted errors.
-- Source waveform mappings cover `SIN` / `SINE`, `PULSE`, `EXP`, `PWL`, `AM`, `SFFM`, and wave-file input. LTspice finite-cycle `PULSE(... Ncycles)` and `SINE(... Ncycles)` are supported, PWL file parsing supports optional header rows, leading blank/comment lines, and space/comma/semicolon/tab delimiters, unsupported PWL repeat syntax produces targeted diagnostics, wave-file channel defaults are not inferred, and topology-changing independent-source options synthesize parser helper components.
+- Source waveform mappings cover `SIN` / `SINE`, `PULSE`, `EXP`, `PWL`, `AM`, `SFFM`, and wave-file input. LTspice finite-cycle `PULSE(... Ncycles)` and `SINE(... Ncycles)` are supported, PWL file parsing supports optional header rows, leading blank/comment lines, and space/comma/semicolon/tab delimiters, simple non-nested LTspice `PWL REPEAT FOR` / `REPEAT FOREVER` blocks are supported, broader PWL variants still produce targeted diagnostics, wave-file channel defaults are not inferred, and topology-changing independent-source options synthesize parser helper components.
 - MOS model generation currently covers legacy levels 1, 2, and 3. LTspice `VDMOS` and advanced monolithic levels such as BSIM/EKV/HiSIM variants are runtime or intentional-unsupported candidates.
 - Distributed-line support currently starts from lossless `T`. LTspice lossy `O` / `LTRA` and uniform RC-line `URC` models need engine triage before runnable support is claimed.
 - P3 LTspice mode maps R/C model `tc=a[,b]`, switch `von`/`voff`, and current-switch `ion`/`ioff` aliases where they lower to existing parameters.
@@ -212,7 +212,8 @@ Implemented P2 behavior:
 - Added LTspice-style smooth limiting support for `uplim(...)` and `dnlim(...)`, while keeping unary `~` as a targeted diagnostic.
 - Added six-argument `EXP(v1 v2 td1 tau1 td2 tau2)` source waveform support with argument-count and positive-tau diagnostics.
 - Added LTspice-mode finite-cycle `PULSE(... Ncycles)` and `SINE(... Ncycles)` support with targeted diagnostics for invalid period/frequency and cycle-count arguments.
-- Added PWL file fixtures for supported local two-column text variants with optional header rows, leading blank/comment lines, and space/comma/semicolon/tab delimiters, plus targeted diagnostics for missing files, empty files, missing data rows, malformed rows, and unsupported LTspice repeat syntax.
+- Added PWL file fixtures for supported local two-column text variants with optional header rows, leading blank/comment lines, and space/comma/semicolon/tab delimiters, plus targeted diagnostics for missing files, empty files, missing data rows, and malformed rows.
+- Added LTspice-mode support for simple non-nested `PWL REPEAT FOR <n>` and `REPEAT FOREVER` blocks with local repeat times, analytic transient fixtures, malformed-repeat diagnostics, and optional LTspice-backed transient golden evidence for `REPEAT FOR`.
 - Added LTspice-mode `tbl=(expr,x1,y1,...)` independent-source lowering to the existing behavioral `table(...)` path.
 - Improved `wavefile=<path> chan=<n> [amplitude=<value>]` validation so missing `wavefile`, missing `chan`, missing files, and invalid `chan` values produce targeted diagnostics.
 - Added LTspice-mode parser synthesis for topology-changing independent-source options: `Rser` adds a series resistor, `Cpar` adds a shunt capacitor, `load` adds a shunt resistor, and `R=<value>` maps to series resistance on voltage sources or load resistance on current sources.
@@ -221,7 +222,7 @@ Remaining follow-up:
 
 - Compare existing random functions with LTspice semantics before making numeric claims.
 - Decide whether LTspice boolean XOR can be added without breaking existing `^` exponent behavior.
-- Defer LTspice PWL repeat variants until fixture-backed runtime behavior is specified.
+- Defer nested/combined LTspice PWL specs, trigger restarts, time/value scale factors, `SCOPEDATA`, and relative `+time` points until fixture-backed runtime behavior is specified.
 
 Acceptance criteria:
 

src/SpiceSharpParser.IntegrationTests/LTspiceCompatibility/LTspiceCompatibilityP2Tests.cs

@@ -131,10 +131,70 @@ public void When_LtspicePwlFileUsesSupportedTextVariant_Expect_TransientReferenc
             }
         }
 
+        [Fact]
+        public void When_LtspicePwlRepeatForIsRead_Expect_ExpandedTransientReferenceValues()
+        {
+            var model = GetSpiceSharpModelWithCompatibility(
+                CompatibilityOptions.LTspice,
+                "LTspice P2 - PWL repeat for",
+                "V1 out 0 PWL REPEAT FOR 3 (1n,1,3n,3) ENDREPEAT",
+                "R1 out 0 1k",
+                ".tran 0.5n 9.5n",
+                ".save V(out)",
+                ".end");
+
+            AssertNoValidationIssues(model.ValidationResult);
+
+            var exports = RunTransientSimulation(model, "V(out)");
+            Assert.NotEmpty(exports);
+            Assert.True(EqualsWithTol(exports, PwlRepeatForReference));
+        }
+
+        [Fact]
+        public void When_LtspicePwlRepeatForeverIsRead_Expect_RepeatingTransientReferenceValues()
+        {
+            var model = GetSpiceSharpModelWithCompatibility(
+                CompatibilityOptions.LTspice,
+                "LTspice P2 - PWL repeat forever",
+                "V1 out 0 PWL REPEAT FOREVER (0,0,1n,1,2n,0) ENDREPEAT",
+                "R1 out 0 1k",
+                ".tran 0.5n 5n",
+                ".save V(out)",
+                ".end");
+
+            AssertNoValidationIssues(model.ValidationResult);
+
+            var exports = RunTransientSimulation(model, "V(out)");
+            Assert.NotEmpty(exports);
+            Assert.True(EqualsWithTol(exports, PwlRepeatTriangleReference));
+        }
+
+        [Theory]
+        [InlineData("V1 out 0 PWL REPEAT FOR 2 (0,0,1n,1,2n,0) ENDREPEAT")]
+        [InlineData("V1 out 0 PWL REPEAT for=2 (0,0,1n,1,2n,0) ENDREPEAT")]
+        [InlineData("V1 out 0 PWL repeat=2 (0,0,1n,1,2n,0) endrepeat")]
+        public void When_LtspicePwlRepeatCountVariantIsRead_Expect_FiniteRepeat(string sourceLine)
+        {
+            var model = GetSpiceSharpModelWithCompatibility(
+                CompatibilityOptions.LTspice,
+                "LTspice P2 - PWL repeat count variant",
+                sourceLine,
+                "R1 out 0 1k",
+                ".tran 0.5n 5n",
+                ".save V(out)",
+                ".end");
+
+            AssertNoValidationIssues(model.ValidationResult);
+
+            var exports = RunTransientSimulation(model, "V(out)");
+            Assert.NotEmpty(exports);
+            Assert.True(EqualsWithTol(exports, PwlFiniteRepeatTriangleReference));
+        }
+
         [Theory]
         [InlineData("V1 out 0 PWL file=\"missing.txt\"", "does not exist")]
-        [InlineData("V1 out 0 PWL repeat 0 0 1n 1 endrepeat", "repeat")]
-        public void When_LtspicePwlFileOrRepeatSyntaxIsUnsupported_Expect_TargetedError(string sourceLine, string expectedMessage)
+        [InlineData("V1 out 0 PWL repeat 0 0 1n 1 endrepeat", "FOR")]
+        public void When_LtspicePwlFileOrBareRepeatSyntaxIsInvalid_Expect_TargetedError(string sourceLine, string expectedMessage)
         {
             var tempDirectory = CreateTempDirectory();
 
@@ -160,6 +220,30 @@ public void When_LtspicePwlFileOrRepeatSyntaxIsUnsupported_Expect_TargetedError(
             }
         }
 
+        [Theory]
+        [InlineData("V1 out 0 PWL REPEAT FOR 2 (0,0,1n,0)", "ENDREPEAT")]
+        [InlineData("V1 out 0 PWL REPEAT FOR 0 (0,0,1n,0) ENDREPEAT", "repeat count")]
+        [InlineData("V1 out 0 PWL REPEAT FOR 2 (0,0,1n) ENDREPEAT", "time/value")]
+        [InlineData("V1 out 0 PWL REPEAT FOR 2 (0,0,0,0) ENDREPEAT", "increasing")]
+        [InlineData("V1 out 0 PWL REPEAT FOR 2 (0,0,1n,1) ENDREPEAT", "contradictory")]
+        [InlineData("V1 out 0 PWL REPEAT FOR 2 (0,0,+1n,0) ENDREPEAT", "relative")]
+        [InlineData("V1 out 0 PWL ENDREPEAT", "requires")]
+        public void When_LtspicePwlRepeatSyntaxIsMalformed_Expect_TargetedError(string sourceLine, string expectedMessage)
+        {
+            var model = GetSpiceSharpModelWithCompatibility(
+                CompatibilityOptions.LTspice,
+                "LTspice P2 - malformed PWL repeat",
+                sourceLine,
+                "R1 out 0 1k",
+                ".tran 1n 6n",
+                ".save V(out)",
+                ".end");
+
+            Assert.True(model.ValidationResult.HasError);
+            AssertErrorContains(model.ValidationResult, "PWL");
+            AssertErrorContains(model.ValidationResult, expectedMessage);
+        }
+
         [Theory]
         [InlineData("", "empty")]
         [InlineData("time,value", "no data")]
@@ -625,6 +709,56 @@ private static double PwlFileReference(double time)
             return Math.Max(0.0, (2e-9 - time) / 1e-9);
         }
 
+        private static double PwlRepeatForReference(double time)
+        {
+            const double period = 3e-9;
+            const double firstPointTime = 1e-9;
+            const double stopTime = 9e-9;
+
+            if (time >= stopTime)
+            {
+                return 3.0;
+            }
+
+            var cycle = (int)Math.Floor(time / period);
+            var localTime = time - (cycle * period);
+            if (localTime < firstPointTime)
+            {
+                if (cycle == 0)
+                {
+                    return 1.0;
+                }
+
+                return 3.0 + ((1.0 - 3.0) * localTime / firstPointTime);
+            }
+
+            return 1.0 + ((3.0 - 1.0) * (localTime - firstPointTime) / (period - firstPointTime));
+        }
+
+        private static double PwlRepeatTriangleReference(double time)
+        {
+            const double halfPeriod = 1e-9;
+            const double period = 2e-9;
+            var localTime = time % period;
+            if (localTime <= halfPeriod)
+            {
+                return localTime / halfPeriod;
+            }
+
+            return (period - localTime) / halfPeriod;
+        }
+
+        private static double PwlFiniteRepeatTriangleReference(double time)
+        {
+            const double stopTime = 4e-9;
+            if (time >= stopTime)
+            {
+                return 0.0;
+            }
+
+            return PwlRepeatTriangleReference(time);
+        }
+
         public static IEnumerable<object[]> PwlFileFormatCases()
         {
             yield return new object[]