Initial commit

.gitignore

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+build/
+pureoption-example

Makefile

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+CC = gcc
+CCFLAGS = -Wall
+BUILDDIR = build
+SRCS = pureoption-example.c pureoption.c
+OBJS = $(addprefix $(BUILDDIR)/, $(patsubst %.c,%.o,$(SRCS)))
+OUT = pureoption-example
+
+.PHONY: all format clean
+.PRECIOUS: $(BUILDDIR)/. $(BUILDDIR)%/.
+
+all: $(OUT)
+
+debug: CCFLAGS += -g
+debug: all
+
+$(BUILDDIR)/.:
+	mkdir -p $@
+
+$(BUILDDIR)%/.:
+	mkdir -p $@
+
+$(OUT): $(OBJS)
+	$(CC) $^ -o $(OUT) $(LDFLAGS)
+
+.SECONDEXPANSION:
+
+$(BUILDDIR)/%.o: %.c | $$(@D)/.
+	$(CC) $(CCFLAGS) -c $< -o $@
+
+format:
+	clang-format -i *.c *.h
+
+clean:
+	rm -rf $(BUILDDIR)
+	rm -f $(OUT)

pureoption-example.c

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+#include "pureoption.h"
+#include <stdio.h>
+
+int main(void) {
+  pureoption opt = pureoption_some(3);
+
+  printf("pureoption_some(3)\n");
+  printf("\thas value: %s\n", pureoption_has(opt) == 1 ? "yes" : "no");
+  printf("\tvalue: %d\n", pureoption_get(int, opt));
+
+  opt = pureoption_none();
+
+  printf("pureoption_none\n");
+  printf("\thas value: %s\n", pureoption_has(opt) == 1 ? "yes" : "no");
+}

pureoption.c

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+#include "pureoption.h"
+#include <stddef.h>
+
+inline static pureoption __pureoption_new(bool has_value, void *value) {
+  pureoption result = {
+      .has_value = has_value,
+      .value = value,
+  };
+
+  return result;
+}
+
+pureoption _pureoption_some(void *value) {
+  return __pureoption_new(true, value);
+}
+
+pureoption pureoption_none(void) { return __pureoption_new(false, NULL); }
+
+bool pureoption_has(pureoption option) { return option.has_value; }
+
+bool pureoption_lacks(pureoption option) { return !option.has_value; }
+
+void *_pureoption_get(pureoption option) { return option.value; }

pureoption.h

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+#ifndef PUREOPTION_H
+#define PUREOPTION_H
+
+#include <stdbool.h>
+
+#define pureoption_some(x)                                                     \
+  ({                                                                           \
+    static typeof(x) _temp = (x);                                              \
+    _pureoption_some(&_temp);                                                  \
+  })
+
+#define pureoption_get(x_type, x) *(x_type *)_pureoption_get(x)
+
+typedef struct {
+  bool has_value;
+  void *value;
+} pureoption;
+
+pureoption _pureoption_some(void *value);
+pureoption pureoption_none(void);
+bool pureoption_has(pureoption option);
+bool pureoption_lacks(pureoption option);
+void *_pureoption_get(pureoption option);
+
+#endif // PUREOPTION_H