Lambdas builtins

6 builtins of Soma 3.2.4 in the category Lambdas, with their exact signatures, as soma describe --builtins --json prints them.

• filter
• find
• any
• all
• count
• reduce

filter

filter(list: List, x => Bool) -> List

Keep elements where the lambda returns true (it answers a Bool; () counts as false).

deterministic · replay: pure

Used in verified programs:

• agents/horde_audit, line 34: let high = verdicts.values() |> filter(v => v.risk == "high")
• finance/portfolio_pnl, line 44: return enriched() |> filter(p => p.pnl > 0.0)
• medical/prescription_lockout, line 88: let kept = filter(current, d => d != drug)
• records/employees, line 33: let rows = staff() |> filter(e => e.dept == dept)

find

find(list: List, x => Bool) -> Any

First element where the lambda returns true, or ().

deterministic · replay: pure

Used in verified programs:

• records/ecs, line 42: let e = es |> find(x => x.id == id)
• records/inventory, line 23: let it = stock() |> find(i => i.sku == sku)
• records/students, line 28: let s = roster() |> find(x => x.name == name)

any

any(list: List, x => Bool) -> Bool

True if the lambda returns true for at least one element.

deterministic · replay: pure

Used in verified programs:

• games/pig_dice, line 22: if any(rolls, r => r == 1) { return 0 }
• games/snake, line 21: return any(snake, seg => seg.y == y && seg.x == x)
• games/yahtzee, line 35: if any(c, x => x >= n) { return sum(dice) }
• medical/bloodbank, line 63: return any(recips, r => r == recipient)

all

all(list: List, x => Bool) -> Bool

True if the lambda returns true for every element (true on empty).

deterministic · replay: pure

Used in verified programs:

• games/tic_tac_toe, line 29: return all(board, c => c != "")

count

count(list: List, x => Bool) -> Int

Number of elements where the lambda returns true.

deterministic · replay: pure

Used in verified programs:

• data/ab_test, line 24: let conv = rows |> count(r => r.converted == 1)
• records/ecs, line 37: return world() |> count(e => e.hp.cur > 0)
• records/employees, line 25: return staff() |> count(e => e.dept == dept)
• records/kanban, line 38: "todo", count(vals, c => c.col == "todo"),

reduce

reduce(list: List, initial, p => expr) -> Any

Fold the list; the lambda receives {acc, val} and returns the next acc.

deterministic · replay: pure

Used in verified programs:

• data/group_reduce, line 26: return votes() |> reduce(0, p => p.acc + p.val.weight)
• math/gcd_lcm, line 25: return xs |> reduce(0, p => gcd(p.acc, p.val))