1 files changed, 28 insertions, 0 deletions
diff --git a/src/parser.js b/src/parser.js
new file mode 100644
index 0000000..a15c8e2
--- /dev/null
+++ b/src/parser.js
@@ -0,0 +1,28 @@
+import * as wrapper from "../src/wrapper.js"
+import * as either from "../src/either.js"
+
+export const show = either =>
+    either(v => "Error: " + v)(v => v(cur => rst => ({ cur, rst })))
+
+export const unit = cur => rst => either.Right(s => s(cur)(rst))
+export const bind = p => f => s => either.bind(p(s))(right => right(cur => rst => f(cur)(rst)))
+
+export const DO = wrapper.DO(unit, bind)
+
+export const satisfy = pred => s => {
+    if (s === "") return either.Left("end of input")
+    const head = s[0]
+    const tail = s.slice(1)
+    return pred(head) ? either.Right(s => s(head)(tail))
+                      : either.Left("unexpected " + head)
+}
+
+export const char = ch => satisfy(c => c == ch)
+
+export const string = str => DO(function* () {
+    const head = str[0]
+    const tail = str.slice(1)
+    yield char(head)
+    return yield tail === "" ? unit(str)
+                             : bind(string(tail))(_ => unit(str))
+})