From a2822926040c39285760b2ca2d350fe8229ac177 Mon Sep 17 00:00:00 2001
From: "Johan B.W. de Vries" <info@jbwdevries.nl>
Date: Sun, 25 Jan 2026 12:47:58 +0100
Subject: [PATCH] Adds strlen as a builtin function

---
 0-lang0py/lang0py.py                          |  5 ++++
 1-lang0py/lang0py.lang0                       |  5 ++++
 2-lang0c/lang0c.lang0                         | 14 +++++++++++
 README.md                                     |  4 ++++
 tests/test_stdlib_functions/test_add.lang0    | 11 ---------
 .../test_strlen.exp.stdout                    |  4 ++++
 tests/test_stdlib_functions/test_strlen.lang0 | 23 +++++++++++++++++++
 7 files changed, 55 insertions(+), 11 deletions(-)
 create mode 100644 tests/test_stdlib_functions/test_strlen.exp.stdout
 create mode 100644 tests/test_stdlib_functions/test_strlen.lang0

diff --git a/0-lang0py/lang0py.py b/0-lang0py/lang0py.py
index f4c5a99..cea3e4c 100644
--- a/0-lang0py/lang0py.py
+++ b/0-lang0py/lang0py.py
@@ -475,6 +475,9 @@ def emitheader():
     emitln("    sys.stderr.flush()")
     emitln("    exit(1)")
     emitln("")
+    emitln("def __strlen(a: str) -> str:")
+    emitln("    return str(len(a))")
+    emitln("")
     emitln("# ### END OF RUNTIME ### #")
     emitln("")
 
@@ -518,6 +521,8 @@ def main():
     mapsetkey("REGISTERID", "stdincolno", "__stdincolno")
     mapsetkey("FUNCREG", "stdinlineno", "1")
     mapsetkey("REGISTERID", "stdinlineno", "__stdinlineno")
+    mapsetkey("FUNCREG", "strlen", "1")
+    mapsetkey("REGISTERID", "strlen", "__strlen")
 
     while True:
         if eof == peek():
diff --git a/1-lang0py/lang0py.lang0 b/1-lang0py/lang0py.lang0
index 0a207e4..abea5db 100644
--- a/1-lang0py/lang0py.lang0
+++ b/1-lang0py/lang0py.lang0
@@ -534,6 +534,9 @@ emitheader:
 	emitln "    sys.stderr.flush()"
 	emitln "    exit(1)"
 	emitln ""
+	emitln "def __strlen(a: str) -> str:"
+	emitln "    return str(len(a))"
+	emitln ""
 	emitln "# ### END OF RUNTIME ### #"
 	emitln ""
 /
@@ -579,6 +582,8 @@ main:
 	mapsetkey "REGISTERID" "stdincolno" "__stdincolno"
 	mapsetkey "FUNCREG" "stdinlineno" "1"
 	mapsetkey "REGISTERID" "stdinlineno" "__stdinlineno"
+	mapsetkey "FUNCREG" "strlen" "1"
+	mapsetkey "REGISTERID" "strlen" "__strlen"
 
 
 	forever
diff --git a/2-lang0c/lang0c.lang0 b/2-lang0c/lang0c.lang0
index edb1aaa..a297535 100644
--- a/2-lang0c/lang0c.lang0
+++ b/2-lang0c/lang0c.lang0
@@ -798,6 +798,18 @@ emitheader:
 	emitln ";"
 	emitln "}"
 	emitln ""
+	emitln "char * __strlen(char * inp)"
+	emitln "{"
+	emitln "    char * buffer = malloc(20);"
+	emitln "    size_t len = strlen(inp);"
+	emit "    snprintf(buffer, 20, "
+	emit quote
+	emit "%zu"
+	emit quote
+	emitln ", len);"
+	emitln "    return buffer;"
+	emitln "}"
+	emitln ""
 	emitln "// ### END OF RUNTIME ### //"
 	emitln ""
 	return
@@ -852,6 +864,8 @@ main:
 	mapsetkey "REGISTERID" "stdincolno" "__stdincolno"
 	mapsetkey "FUNCREG" "stdinlineno" "1"
 	mapsetkey "REGISTERID" "stdinlineno" "__stdinlineno"
+	mapsetkey "FUNCREG" "strlen" "1"
+	mapsetkey "REGISTERID" "strlen" "__strlen"
 
 	forever
 		calc char peek
diff --git a/README.md b/README.md
index 24a3656..7d66304 100644
--- a/README.md
+++ b/README.md
@@ -194,6 +194,10 @@ Returns the column number for stdin (starting at 1)
 
 Returns the line number for stdin (starting at 1)
 
+#### strlen a
+
+Returns a string with the length of a.
+
 ### Typing
 
 Every variable is of type string. Every function gets a number of strings as output, and returns another string.
diff --git a/tests/test_stdlib_functions/test_add.lang0 b/tests/test_stdlib_functions/test_add.lang0
index 0b63293..d7721df 100644
--- a/tests/test_stdlib_functions/test_add.lang0
+++ b/tests/test_stdlib_functions/test_add.lang0
@@ -1,14 +1,3 @@
-func tst a b:
-	declare var
-	calc var add a b
-	emit a
-	emit " + "
-	emit b
-	emit " = "
-	emit var
-	emit eol
-/
-
 main:
 	declare var
 
diff --git a/tests/test_stdlib_functions/test_strlen.exp.stdout b/tests/test_stdlib_functions/test_strlen.exp.stdout
new file mode 100644
index 0000000..3daeb47
--- /dev/null
+++ b/tests/test_stdlib_functions/test_strlen.exp.stdout
@@ -0,0 +1,4 @@
+strlen()=0
+strlen()=1
+strlen()=1
+strlen()=8
diff --git a/tests/test_stdlib_functions/test_strlen.lang0 b/tests/test_stdlib_functions/test_strlen.lang0
new file mode 100644
index 0000000..98dbe7d
--- /dev/null
+++ b/tests/test_stdlib_functions/test_strlen.lang0
@@ -0,0 +1,23 @@
+main:
+	declare var
+
+	calc var strlen ""
+	emit "strlen()="
+	emit var
+	emit eol
+
+	calc var strlen "0"
+	emit "strlen()="
+	emit var
+	emit eol
+
+	calc var strlen "1"
+	emit "strlen()="
+	emit var
+	emit eol
+
+	calc var strlen "abcdefgh"
+	emit "strlen()="
+	emit var
+	emit eol
+/