diff --git a/README.md b/README.md
index 5b46b3e..1af11af 100644
--- a/README.md
+++ b/README.md
@@ -37,6 +37,10 @@ Bash library which provides utility functions and helpers for functional program
   - [collection::every()](#collectionevery)
   - [collection::filter()](#collectionfilter)
   - [collection::find()](#collectionfind)
+  - [collection::invoke()](#collectioninvoke)
+  - [collection::map()](#collectionmap)
+  - [collection::reject()](#collectionreject)
+  - [collection::some()](#collectionsome)
 - [Date](#date)
   - [date::now()](#datenow)
   - [date::epoc()](#dateepoc)
@@ -524,7 +528,7 @@ collection::each "test_func"  <<< "${out[@]}"
 
 - **0**:  If successful.
 - **2**: Function missing arguments.
-- other exitcode returned by iteratee
+- other exitcode returned by iteratee.
 
 #### Output on stdout
 
@@ -594,7 +598,7 @@ check_a(){
     [[ "$1" = "a" ]]
 }
 printf "%s\n" "${arr[@]}" | collection::find "check_a"
-#output
+#Output
 a
 ```
 
@@ -612,6 +616,116 @@ a
 
 - first array value matching the iteratee function.
 
+### collection::invoke()
+
+Invokes the iteratee with each element passed as argument to the iteratee.
+Input to the function can be a pipe output, here-string or file.
+
+#### Example
+
+```bash
+opt=("-a" "-l")
+printf "%s\n" "${opt[@]}" | collection::invoke "ls"
+```
+
+#### Arguments
+
+- **$1** (string): Iteratee function.
+
+#### Exit codes
+
+- **0**:  If successful.
+- **2**: Function missing arguments.
+- other exitcode returned by iteratee.
+
+#### Output on stdout
+
+- Output from the iteratee function.
+
+### collection::map()
+
+Creates an array of values by running each element in array through iteratee.
+Input to the function can be a pipe output, here-string or file.
+
+#### Example
+
+```bash
+arri=("1" "2" "3")
+add_one(){
+  i=${1}
+  i=$(( i + 1 ))
+  printf "%s\n" "$i"
+}
+printf "%s\n" "${arri[@]}" | collection::map "add_one"
+```
+
+#### Arguments
+
+- **$1** (string): Iteratee function.
+
+#### Exit codes
+
+- **0**:  If successful.
+- **2**: Function missing arguments.
+- other exitcode returned by iteratee.
+
+#### Output on stdout
+
+- Output result of iteratee on value.
+
+### collection::reject()
+
+The opposite of filter function; this method returns the elements of collection that iteratee does not return true.
+Input to the function can be a pipe output, here-string or file.
+
+#### Example
+
+```bash
+arri=("1" "2" "3" "a")
+printf "%s\n" "${arri[@]}" | collection::reject "variable::is_numeric"
+#Ouput
+a
+```
+
+#### Arguments
+
+- **$1** (string): Iteratee function.
+
+#### Exit codes
+
+- **0**:  If successful.
+- **2**: Function missing arguments.
+
+#### Output on stdout
+
+- array values not matching the iteratee function.
+
+#### See also
+
+- [collection::filter](#collection::filter)
+
+### collection::some()
+
+Checks if iteratee returns true for any element of the array.
+Input to the function can be a pipe output, here-string or file.
+
+#### Example
+
+```bash
+arr=("a" "b" "3" "a")
+printf "%s\n" "${arr[@]}" | collection::reject "variable::is_numeric"
+```
+
+#### Arguments
+
+- **$1** (string): Iteratee function.
+
+#### Exit codes
+
+- **0**:  If match successful.
+- **1**: If no match found.
+- **2**: Function missing arguments.
+
 ## Date
 
 Functions for manipulating dates.
diff --git a/src/collection.sh b/src/collection.sh
index 6d1e75c..bc0de63 100644
--- a/src/collection.sh
+++ b/src/collection.sh
@@ -29,7 +29,7 @@
 #
 # @exitcode 0  If successful.
 # @exitcode 2 Function missing arguments.
-# @exitcode other exitcode returned by iteratee
+# @exitcode other exitcode returned by iteratee.
 #
 # @stdout Output of iteratee function.
 collection::each() {
@@ -122,7 +122,7 @@ collection::filter() {
 #       [[ "$1" = "a" ]]
 #   }
 #   printf "%s\n" "${arr[@]}" | collection::find "check_a"
-#   #output
+#   #Output
 #   a
 #
 # @arg $1 string Iteratee function.
@@ -132,7 +132,109 @@ collection::filter() {
 # @exitcode 2 Function missing arguments.
 #
 # @stdout first array value matching the iteratee function.
-function collection::find() {
+collection::find() {
+    [[ $# = 0 ]] && printf "%s: Missing arguments\n" "${FUNCNAME[0]}" && return 2
+    declare func="${@}"
+    declare IFS=$'\n'
+    while read -r it; do
+
+        if [[ "${func}" == *"$"* ]]; then
+            eval "${func}"
+        else
+            eval "${func}" "'${it}'"
+        fi
+        declare -i ret="$?"
+        if [[ $ret = 0 ]]; then
+            printf "%s" "${it}"
+            return 0
+        fi
+    done
+
+    return 1
+}
+
+# @description Invokes the iteratee with each element passed as argument to the iteratee.
+# Input to the function can be a pipe output, here-string or file.
+# @example
+#   opt=("-a" "-l")
+#   printf "%s\n" "${opt[@]}" | collection::invoke "ls"
+#
+# @arg $1 string Iteratee function.
+#
+# @exitcode 0  If successful.
+# @exitcode 2 Function missing arguments.
+# @exitcode other exitcode returned by iteratee.
+#
+# @stdout Output from the iteratee function.
+collection::invoke() {
+    [[ $# = 0 ]] && printf "%s: Missing arguments\n" "${FUNCNAME[0]}" && return 2
+    declare -a args=()
+    declare func="${@}"
+    while read -r it; do
+        args=("${args[@]}" "$it")
+    done
+
+    eval "${func}" "${args[@]}"
+}
+
+# @description Creates an array of values by running each element in array through iteratee.
+# Input to the function can be a pipe output, here-string or file.
+# @example
+#   arri=("1" "2" "3")
+#   add_one(){
+#     i=${1}
+#     i=$(( i + 1 ))
+#     printf "%s\n" "$i"
+#   }
+#   printf "%s\n" "${arri[@]}" | collection::map "add_one"
+#
+# @arg $1 string Iteratee function.
+#
+# @exitcode 0  If successful.
+# @exitcode 2 Function missing arguments.
+# @exitcode other exitcode returned by iteratee.
+#
+# @stdout Output result of iteratee on value.
+collection::map() {
+    [[ $# = 0 ]] && printf "%s: Missing arguments\n" "${FUNCNAME[0]}" && return 2
+    declare func="${@}"
+    declare IFS=$'\n'
+    declare out
+
+    while read -r it; do
+
+        if [[ "${func}" == *"$"* ]]; then
+            out="$("${func}")"
+        else
+            out="$("${func}" "$it")"
+        fi
+
+        declare -i ret=$?
+
+        if [[ $ret -ne 0 ]]; then
+            return $ret
+        fi
+
+        printf "%s\n" "${out}"
+    done
+}
+
+# @description The opposite of filter function; this method returns the elements of collection that iteratee does not return true.
+# Input to the function can be a pipe output, here-string or file.
+# @example
+#   arri=("1" "2" "3" "a")
+#   printf "%s\n" "${arri[@]}" | collection::reject "variable::is_numeric"
+#   #Ouput
+#   a
+#
+# @arg $1 string Iteratee function.
+#
+# @exitcode 0  If successful.
+# @exitcode 2 Function missing arguments.
+#
+# @stdout array values not matching the iteratee function.
+# @see collection::filter
+collection::reject() {
     [[ $# = 0 ]] && printf "%s: Missing arguments\n" "${FUNCNAME[0]}" && return 2
     declare func="${@}"
     declare IFS=$'\n'
@@ -143,9 +245,40 @@ function collection::find() {
         else
             eval "${func}" "'$it'"
         fi
-        declare -i ret="$?"
-        if [[ $ret = 0 ]]; then
+        declare -i ret=$?
+        if [[ $ret -ne 0 ]]; then
             echo "$it"
+        fi
+
+    done
+}
+
+# @description Checks if iteratee returns true for any element of the array.
+# Input to the function can be a pipe output, here-string or file.
+# @example
+#   arr=("a" "b" "3" "a")
+#   printf "%s\n" "${arr[@]}" | collection::reject "variable::is_numeric"
+#
+# @arg $1 string Iteratee function.
+#
+# @exitcode 0  If match successful.
+# @exitcode 1 If no match found.
+# @exitcode 2 Function missing arguments.
+collection::some() {
+    [[ $# = 0 ]] && printf "%s: Missing arguments\n" "${FUNCNAME[0]}" && return 2
+    declare func="${@}"
+    declare IFS=$'\n'
+    while read -r it; do
+
+        if [[ "${func}" == *"$"* ]]; then
+            eval "${func}"
+        else
+            eval "${func}" "'$it'"
+        fi
+
+        declare -i ret=$?
+
+        if [[ $ret -eq 0 ]]; then
             return 0
         fi
     done