finish merge ugh

README.md

@@ -1,3 +1,75 @@
 clojure matrix-repl thing, the last two methods in src/matrix/core.clj are the only interesting bits
 
 src/matrix/core.clj is the only file with interesting stuff
+
+\*actual\* usage example:
+```
+matrix.core=> (matrix-repl [[1 1 -1 -5] [5 -1 1 -1] [-1 3 -2 1]] :yeah)
+┏               ┓
+┃  1  1 -1 │ -5 ┃
+┃  5 -1  1 │ -1 ┃
+┃ -1  3 -2 │  1 ┃
+┗               ┛
+(add-mul 5 2 1)
+┏               ┓
+┃  1  1 -1 │ -5 ┃
+┃  0 14 -9 │  4 ┃
+┃ -1  3 -2 │  1 ┃
+┗               ┛
+(add 0 2)
+┏               ┓
+┃  1  1 -1 │ -5 ┃
+┃  0 14 -9 │  4 ┃
+┃  0  4 -3 │ -4 ┃
+┗               ┛
+(add-mul -4/14 1 2)
+┏                           ┓
+┃     1     1    -1 │    -5 ┃
+┃     0    14    -9 │     4 ┃
+┃     0     0  -3/7 │ -36/7 ┃
+┗                           ┛
+(mul 7 2)
+┏                   ┓
+┃   1   1  -1 │  -5 ┃
+┃   0  14  -9 │   4 ┃
+┃   0   0  -3 │ -36 ┃
+┗                   ┛
+(mul -1/3 2)
+┏               ┓
+┃  1  1 -1 │ -5 ┃
+┃  0 14 -9 │  4 ┃
+┃  0  0  1 │ 12 ┃
+┗               ┛
+(add-mul 9 2 1)
+┏                   ┓
+┃   1   1  -1 │  -5 ┃
+┃   0  14   0 │ 112 ┃
+┃   0   0   1 │  12 ┃
+┗                   ┛
+(mul 1/14 1)
+┏               ┓
+┃  1  1 -1 │ -5 ┃
+┃  0  1  0 │  8 ┃
+┃  0  0  1 │ 12 ┃
+┗               ┛
+(add 2 0)
+┏               ┓
+┃  1  1  0 │  7 ┃
+┃  0  1  0 │  8 ┃
+┃  0  0  1 │ 12 ┃
+┗               ┛
+(add-mul -1 1 0)
+┏               ┓
+┃  1  0  0 │ -1 ┃
+┃  0  1  0 │  8 ┃
+┃  0  0  1 │ 12 ┃
+┗               ┛
+print-equations
+x = -1
+y = 8
+z = 12
+┏               ┓
+┃  1  0  0 │ -1 ┃
+┃  0  1  0 │  8 ┃
+┃  0  0  1 │ 12 ┃
+┗               ┛

src/matrix/core.clj

@@ -135,10 +135,68 @@
    m))
 
 ;; repl commands
+(defn fmt-num
+  "Format a number, empty string for 1"
+  [n]
+  (if (= 1 n)
+    ""
+    (str n)))
+
+(defn mid-sign
+  "Format a term as either '+ n' or '- n'"
+  [n]
+  (if (pos? n)
+    (str "+ " (fmt-num n))
+    (str "- " (fmt-num (* -1 n)))))
+
+(defn single-term
+  [val name first]
+  (if (zero? val)
+    ""
+    (str (if first
+           (fmt-num val)
+           (mid-sign val))
+         name)))
+
+; could be generalized
+(defn equation-from-row
+  "Write a pretty equation from one row of an augmented matrix"
+  ([row] (apply equation-from-row row))
+  ([x eq] (str (single-term x "x" true)
+               " = "
+               eq))
+  ([x y eq]
+   (let [x (single-term x "x" true)
+         y (single-term y "y" (empty? x))]
+     (str x
+          (if (not-empty x) " ")
+          y
+          (if (not-empty y) " ")
+          "= " eq)))
+  ([x y z eq]
+   (let [x (single-term x "x" true)
+         y (single-term y "y" (empty? x))
+         z (single-term z "z" (and (empty? x) (empty? y)))]
+     (str x
+          (if (not-empty x) " ")
+          y
+          (if (not-empty y) " ")
+          z
+          (if (not-empty z) " ")
+          "= " eq))))
+
+(defn print-matrix-equations
+  [m]
+  (do
+    (last (for [row m]
+            (println (equation-from-row row))))
+    m))
+
 (defn swap    [n m]       #(swap-rows % n m))
 (defn add     [from to]   #(add-rows % from to))
 (defn add-mul [n from to] #(add-rows-with-mul % n from to))
-(defn mul     [n at]      #(mul-row % n at))
+(defn mul [n at] #(mul-row % n at))
+(def  print-equations print-matrix-equations)
 
 (defn apply-input
   [m]
@@ -157,7 +215,6 @@
    (pprint-matrix m add-bar)
    (iterate (comp #(pprint-matrix % add-bar) apply-input) m)))
 
-
 (defn -main
   "I don't do a whole lot ... yet."
   [& args]
@@ -167,3 +224,11 @@
           got)
         matrix-repl
         last)))
+
+; TODO: actual parsing of row operations
+; TODO: parse equations (easy, but requires context (e.g. x = 1 could be any number of variables))
+; TODO: undoing
+  ; will have to have a higher level thing for storing state
+; TODO: solving id-matrix
+; TODO: solving gaussian-eliminated matrix
+; TODO: automation