Miscellaneous Functions

(always x)

Return a function that discards any arguments and always returns x.

(antepenultimate xs)

Get the third-to-last element from an indexed data structure.

(binary-search x arr &opt <?)

Returns the index of x in a sorted array or tuple or the index of the next item if x is not present. This is the correct insert index for x within arr. If a <? comparator is given, the search uses that to compare elements, otherwise uses <.

(binary-search-by x arr f)

Returns the index of x in an array or tuple which has been sorted by a mapping function f, or the index of the next item if x is not present. This is the correct insert index for x within arr.

(caperr & body)

Captures the standard error output of the variadic body and returns it as a buffer.

(capout & body)

Captures the standard output of the variadic body and returns it as a buffer.

(cond-> val & clauses)

Threading conditional macro. It takes val to mutate, and clauses pairs with condition and operation to which val, is passed as first argument. All conditions are tried and for truthy conditions the operation is executed. Returns the value mutated if any condition is truthy.

(cond->> val & clauses)

Threading conditional macro. It takes val to mutate, and clauses pairs of condition and operation to which val, is passed as last argument. All conditions are tried and for truthy conditions the operation is executed. Returns mutated value if any condition is truthy.

(dedent & xs)

Remove indentation after concatenating the arguments. Works by removing leading whitespace, and then removing that same pattern of whitespace after new lines.

(defs & bindings)

Defines many constants as in let bindings, but without creating a new scope.

(dfs data visit-leaf &opt node-before node-after get-children seen)

Do a depth first, pre-order traversal over a data structure. Also allow for callbacks before and after visiting the children of a node. Also allow for a custom get-children function to change traversal as needed. Will detect cycles if an empty table is passed as the seen parameter, which is used to cache values that have been visited.

(do-def c d & body)

Convenience macro for defining constant named c with value d before body and returning it after evaluating body, that presumably modifies the content referred to by c. For example, a buffer, table or array.

(do-var v d & body)

Convenience macro for defining variable named v with value d before body and returning it after evaluating body, that presumably modifies v.

(format-table buf-into data &opt columns header-mapping column-mapping)

Same as print-table but pushes table into a buffer.

(gett ds & keyz)

Recursive macro (get). Similar to get-in, but keyz is variadic.

(insert-sorted arr <? & xs)

Insert elements in arr such that it remains sorted by the comparator. If arr is not sorted beforehand, the results are undefined. Returns arr.

(insert-sorted-by arr f & xs)

Insert elements in arr such that it remains sorted by the value returned when f is called with the element, comparing the values with <. If arr is not sorted beforehand, the results are undefined. Returns arr.

(int->string int &opt base)

Stringify an integer in a particular base. Defaults to decimal (base 10).

(int/ & xs)

Perform integer division.

(log level & args)

Print to a dynamic binding stream if that stream is set, otherwise do nothing. Evaluate to nil. For example, (log :err "value error: %V" my-value) will print to (dyn :err) only if (dyn :err) has been set.

(make prototype & pairs)

Convenience macro for creating new table from even number of kvs pairs in variadic pairs arguments and setting its prototype to prototype. Factory function for creating new objects from prototypes.

(make-id &opt prefix)

Create a random, printable keyword id with 10 bytes of entropy with an optional prefix.

(map-keys f data)

Returns new table with function f applied to data's keys recursively.

(map-keys-flat f data)

Returns new table with function f applied to data's keys without recursing.

(map-vals f data)

Returns new table with function f applied to data's values.

(merge-sorted a b &opt <?)

Merges two sorted arrays so that the result remains sorted, using an optional comparator. If no comparator is given, < is used.

(merge-sorted-by a b f)

Merges two sorted arrays so that result remains sorted when f is called on each element, comparing the values with <.

(penultimate xs)

Get the second-to-last element from an indexed data structure.

(print-table data &opt columns header-mapping column-mapping)

Iterate through the rows of a data structure and print a table in a human readable way, with padding and heading information. Can optionally provide a function used to print a row, as well as optionally select column keys for each row. Lastly, a header-mapping dictionary can be provided that changes the printed header names by mapping column keys to the desired header name. If no mapping is found, then the column key will be used as the header name. Returns nil.

(randomize-array arr &opt rng)

Randomizes array using the fisher-yates shuffle, takes an optional random number generator.

(second xs)

Get the second element from an indexed data structure.

(select-keys data keyz)

Returns new table with selected keyz from dictionary data.

(set* tgts exprs)

Parallel set function. Takes a list of targets and expressions, evaluates all the expressions, and then assigns them to the targets. Each target can be a variable or a 2-tuple, just like in the normal set special form.

(string->int str &opt base)

Parse an integer in the given base. Defaults to decimal (base 10). Differs from scan-number in that this does not recognize floating point notation.

(table-filter pred dict)

Filter a key-value structure into a table. Semantics are the same as for built-in filter, except that pred takes two arguments (key and value). Does not consider prototypes.

(third xs)

Get the third element from an indexed data structure.

(trim-prefix prefix str)

Trim the specified prefix of a string if it has one

(trim-suffix suffix str)

Trim the specified suffix of a string if it has one

(until cnd & body)

Repeat body while the cnd is false. Equivalent to (while (not cnd) ;body).

(vars & bindings)

Defines many variables as in let bindings, but without creating a new scope.