finally a while without files that isn't done better by a for

subject_03_switch_case_default/trafic_light.c

@@ -0,0 +1,166 @@
+/*
+Copyright 2018 Jacques de Hooge, GEATEC engineering, www.geatec.com
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+/*
+This program features 2 statemachines.
+One has 2 states, the other 3.
+They each run at their own pace.
+
+Note that state machines don't have to cycle through a fixed sequence of states.
+They can go through states in arbitrary, dynamically determined order.
+Also state transitions do not need to be triggered by elapsed time intervals.
+The may also be caused by external triggers, like sensor signals changing.
+*/
+
+#include <stdio.h>
+#include <stdbool.h>
+
+#define offBlinkState 0
+#define onBlinkState 1
+
+#define greenPhaseState 0
+#define yellowPhaseState 1
+#define redPhaseState 2
+
+int main () {
+
+    // ====== Yellow blinking traffic light
+
+    int const blinkTime = 3000;
+
+    int oldBlinkState = onBlinkState;
+    int blinkState = offBlinkState;
+
+    bool yellowBlinkLightIsOn = false;
+
+    // ====== Green, yellow and red phase traffic light
+
+    int const phaseTime = 2000;
+
+    int oldPhaseState = redPhaseState;
+    int phaseState = greenPhaseState;
+
+    bool greenPhaseLightIsOn = false;
+    bool yellowPhaseLightIsOn = false;
+    bool redPhaseLightIsOn = false;
+
+    // ====== Initialize start time
+
+    int currentTime = 0;
+    int startBlinkTime = currentTime;
+    int startPhaseTime = startBlinkTime;
+
+    // ====== Main control loop
+
+    printf ("State machines: No SLEEP but ASYNCH!\n");
+    printf ("(Press [ENTER] each time to advance 1 s)\n\n");
+
+    while (true) {
+        // ====== Read out clock only once in the main loop, so there's only one unique time
+
+        // In a realtime environment, the current system time would be retrieved
+        currentTime += 100;
+
+        // ====== Separate state machine for blinking traffic light, has 2 phases
+
+        switch (blinkState) {
+            case offBlinkState:
+                if (blinkState != oldBlinkState) {
+                    // This part only done once after state transition
+                    oldBlinkState = blinkState;
+                }
+
+                // Transition condition continuously monitored
+                if (currentTime - startBlinkTime > blinkTime) {
+                    blinkState = onBlinkState;
+                }
+
+                break;
+
+            case onBlinkState:
+                if (blinkState != oldBlinkState) {
+                    // This part only done once after state transition
+                    oldBlinkState = blinkState;
+                    yellowBlinkLightIsOn = true;
+                }
+
+                // Transition condition continuously monitored
+                if (currentTime - startBlinkTime > 2 * blinkTime) {
+                    blinkState = offBlinkState;
+                    startBlinkTime = currentTime;             
+                    yellowBlinkLightIsOn = false;
+                }
+
+                break;
+        }
+
+        // ====== Separate state machine for red, green, yellow phase traffic light, has 3 phases
+
+        switch (phaseState) {
+            case greenPhaseState:
+                if (phaseState != oldPhaseState) {
+                    // This part only done once after state transition   
+                    oldPhaseState = phaseState;
+                    greenPhaseLightIsOn = true;
+                }
+
+                // Transition condition continuously monitored
+                if (currentTime - startPhaseTime > 2 * phaseTime) {
+                    phaseState = yellowPhaseState;
+                    greenPhaseLightIsOn = false;
+                }
+
+                break;
+
+            case yellowPhaseState:
+                if (phaseState != oldPhaseState) {
+                    // This part only done once after state transition   
+                    oldPhaseState = phaseState;
+                    yellowPhaseLightIsOn = true;
+                }
+
+                // Transition condition continuously monitored
+                if (currentTime - startPhaseTime > 3 * phaseTime) {
+                    phaseState = redPhaseState;
+                    yellowPhaseLightIsOn = false;
+                }
+
+                break;
+
+            case redPhaseState:
+                if (phaseState != oldPhaseState) {
+                    // This part only done once after state transition   
+                    oldPhaseState = phaseState;
+                    redPhaseLightIsOn = true;
+                }
+
+                // Transition condition continuously monitored
+                if (currentTime - startPhaseTime > 5 * phaseTime) {
+                    phaseState = greenPhaseState;
+                    startPhaseTime = currentTime;
+                    redPhaseLightIsOn = false;
+                }
+
+                break;
+        }
+
+        if (currentTime % 1000 == 0) {
+            printf ("%3i s      %c      %c %c %c", currentTime / 1000, yellowBlinkLightIsOn ? 'B' : '.', greenPhaseLightIsOn ? 'G' : '.', yellowPhaseLightIsOn ? 'Y' : '.', redPhaseLightIsOn ? 'R' : '.');
+            char dummy = getchar ();
+        }
+    }
+    return 0;
+}

subject_04_loops/for_nested.c

@@ -0,0 +1,40 @@
+/*
+Copyright 2018 Jacques de Hooge, GEATEC engineering, www.geatec.com
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+#include <stdio.h>
+#include <string.h>
+#include <math.h>
+
+int main () {
+    char action [] = "p";
+
+    for (int base = 0; base < 4; base++) {
+        for (int exponent = 0; exponent < 4; exponent++) {  // Nested "for"s are commonplace and useful
+            if (!strcmp (action, "g")) {
+                goto exit;                                  // Use "goto" ONLY to jump out of inner loop (there are alternatives)
+            }
+            else if (!strcmp (action, "c")) {
+                strcpy (action, "p");
+                continue;                                   // Use of "continue" is rare, in this case it's better to put the loop tail inside an "else" block
+            }
+
+            printf ("%d ^ %d = %f, proceed, continue after next, goto exit <p/c/g>? ", base, exponent, pow (base, exponent));
+            scanf ("%s", action);
+        }  
+    }
+
+    exit: return 0;
+}

subject_04_loops/for_simple.c

@@ -0,0 +1,36 @@
+/*
+Copyright 2018 Jacques de Hooge, GEATEC engineering, www.geatec.com
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+#include <stdio.h>
+#include <string.h>
+#include <math.h>
+
+int main () {
+    char breakOut [] = "n";
+
+    for (int exponent = 0; exponent < 16; exponent++) {
+        if (!strcmp (breakOut, "y")) {
+            break;
+        }
+        else {
+            printf ("2 ^ %d = %f, break out <y/n>? ", exponent, pow (2, exponent));
+        }
+
+        scanf ("%s", breakOut);
+    }
+
+    return 0;
+}

subject_04_loops/while.c

@@ -0,0 +1,31 @@
+/*
+Copyright 2018 Jacques de Hooge, GEATEC engineering, www.geatec.com
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+#include <stdio.h>
+
+int main () {
+    // Almost anything in C (and C++) is an expression!
+    // This allows even a naive compiler to keep things in CPU registers.
+    // It's one of the things that made C (and C++) code fast right from the start.
+    // Not everyone likes this coding style, but then again not everyone likes C...
+
+    float a, b;
+    a = b = 1;
+
+    while ((a *= 1.1) < ++b) {
+        printf ("%f %f\n", a, b);
+    }
+}