diff --git a/src/fn.js b/src/fn.js
index d672e1f..dd9128b 100644
--- a/src/fn.js
+++ b/src/fn.js
@@ -26,7 +26,7 @@ export const always = x => () => x
 export const orDefault = curry((value, defaultValue) => value || defaultValue)
 export const orElse = curry((value, fn) => orDefault(value, fn()))
 export const pipe = (...f) => v => reduce(applyTo, v, f)
-export const apply = fn => args => fn.apply(null, args)
+export const apply = curry((fn, args) => fn.apply(null, args))
 export const applyTo = curry((v, fn) => fn(v))
 export const useWith = curry((fn, tfns) =>
   curryN(
@@ -35,8 +35,8 @@ export const useWith = curry((fn, tfns) =>
   ))
 
 export const converge = (fn, tfns) => curryN(
-  pipe(length, map, max)(tfns),
-  (...args) => fn(...map(tfn => tfn(...args), tfns))
+  pipe(map(length), max)(tfns),
+  (...args) => pipe(map(flip(apply)(args)), apply(fn))(tfns)
 )
 
 export const diverge = (fn, tfns) => pipe(applyTo, flip(map)(tfns), apply(fn))
@@ -67,8 +67,12 @@ export const split = curry((delim, v) => v.split(delim))
 // math
 export const max = v => Math.max(...v)
 export const min = v => Math.min(...v)
-export const inc = v => v + 1
-export const dec = v => v - 1
+export const add = curry((x, y) => x + y)
+export const sub = curry((x, y) => x - y)
+export const mul = curry((x, y) => x * y)
+export const div = curry((x, y) => x / y)
+export const inc = add(1)
+export const dec = sub(1)
 
 // arrays
 export const map = curry((fn, v) => v.map(fn))
@@ -92,6 +96,7 @@ export const append = curry((value, iter) => [...iter, value])
 export const enumerate = value => value.map((v, i) => ([i, v]))
 export const flatten = curry((n, v) => v.flat(n))
 export const update = curry((index, value, arr) => arr.toSpliced(index, 1, value))
+export const sum = reduce(add, 0)
 
 // objects
 const makePath = unless(isArray, split('.'))
@@ -103,18 +108,18 @@ export const assocPath = curry((key, value, obj) => pipe(
   mergeRightDeep(obj),
 )(key))
 
-export const mergeLeftDeep = curry((a, b) =>
+export const mergeRightDeep = curry((a, b) =>
   reduce((acc, key) => pipe(
     ifElse(
       every(is(Object)),
-      apply(mergeLeftDeep),
+      apply(mergeRightDeep),
       last
     ),
     v => assoc(key, v, acc)
   )([acc[key], b[key]]), a, keys(b))
 )
 
-export const mergeRightDeep = flip(mergeLeftDeep)
+export const mergeLeftDeep = flip(mergeRightDeep)
 
 export const prop = curry((key, obj) => obj && key && obj[key])
 export const path = curry((key, obj) => reduce(flip(prop), obj, makePath(key)))