CSV ​

Functions for parsing and encoding CSV (Comma-Separated Values) data. Sema uses the Rust csv crate, which handles RFC 4180 edge cases like quoted fields, embedded commas, and newlines within fields.

Type mapping

All CSV values are returned as strings. Use string/to-number, string/to-symbol, etc. to convert fields to the types you need.

Parsing ​

csv/parse ​

Parse a CSV string into a list of lists (rows of fields). No header processing — every row is returned as-is.

Signature: (csv/parse csv-string) → list

sema
(csv/parse "a,b\n1,2\n3,4")
; => (("a" "b") ("1" "2") ("3" "4"))

Quoted fields with commas and newlines are handled correctly:

sema
(csv/parse "name,bio\n\"Ada\",\"Mathematician, writer\"\n")
; => (("name" "bio") ("Ada" "Mathematician, writer"))

csv/parse-maps ​

Parse a CSV string into a list of maps. The first row is used as headers, which become keyword keys in each map.

Signature: (csv/parse-maps csv-string) → list

sema
(csv/parse-maps "name,age\nAda,36\nBob,25")
; => ({:age "36" :name "Ada"} {:age "25" :name "Bob"})

Access fields by keyword:

sema
(define rows (csv/parse-maps "name,age\nAda,36\nBob,25"))
(:name (first rows))   ; => "Ada"

Encoding ​

csv/encode ​

Encode a list of lists (or vectors) into a CSV string. Each inner list/vector becomes one row. Non-string values are stringified automatically.

Signature: (csv/encode rows) → string

sema
(csv/encode '(("a" "b") ("1" "2")))
; => "a,b\n1,2\n"

Numeric and other values are converted to strings:

sema
(csv/encode '(("name" "score") ("Ada" 100)))
; => "name,score\nAda,100\n"

Examples ​

Round-trip example ​

sema
(define csv-text "name,age\nAda,36\nBob,25\n")
(define parsed (csv/parse csv-text))
(csv/encode parsed)
; => "name,age\nAda,36\nBob,25\n"

Pipeline: file → CSV → processing ​

sema
;; Read a CSV file and extract a column
(define data (csv/parse-maps (file/read "users.csv")))
(map (lambda (row) (:name row)) data)